This proposal is for the purchase of a Zeiss LSM 510 confocal microscope to be used by seven principal investigators and their laboratories in support of eighteen NIH funded projects. These groups will occupy approximately 85% time on the instrument, minor users will have access to the equipment at other times. The requested instrument offers the flexibility of a multi-user microscope that will be the "work horse" for many laboratories. A four-laser microscope is requested (blue diode 405 nm, argon 458, 477, 488 and 514 nm, Hene 543 nm, Hene 633 nm lasers), allowing simultaneous or sequential observation of commonly used blue yellow green, red and far red emitting fluorophores. The instrument will be mounted on a Zeiss 200 Axiovert inverted microscope, equipped with a heated stage motorized in the x, y and z axes. This microscope will provide the flexibility of observation of fixed tissues and cultured cells, as well as observations of dynamic processes in living cells. Objectives are requested to permit the optimal collection of fluorescence signals from fixed tissues and cells, and of cultured cells at an oil/glass/water interface. Software is requested that will permit three-dimensional reconstruction of objects, real time analysis of signal intensities, and sequential collection of z-series from multiple cells in different fields for prolonged periods due to the x/y motorized stage). All of the major users are experienced microscopists, most of whom have previously used confocal microscopy. Existing confocal microscopes in the investigators' laboratories are coming to the end of their useful life and presently require considerable and costly maintenance. Importantly, service contracts will not be offered in the future, requiring availability of a new instrument. Other instruments at UCSF are extensively used by other groups, are not sufficiently flexible for the required uses, or are at other distant campuses. Some of these instruments will be moved to other campuses when faculty relocates to the new UCSF campus at Mission Bay. An impartial faculty committee will oversee use of the microscope. A recharge system will be implemented to fund the routine maintenance and support of the microscope. All users will take a classroom based and hands on training program. Institutional support includes provision of newly refurbished space, funding of technical support for three years, provision of computing support, and fiscal and administrative oversight and support.